BIST plotter: add SOG adjustment to plot STW for RX Noise test

[kjerram]

Speed over ground (SOG) is usually applied (parsed from file name or from SIS 5 BIST data) for RX Noise plots.

Add speed through water (STW) as a test parameter, based on SOG (as parsed) with user-defined adjustment for apparent currents along ship course. For example, if SOG = 10 kts (parsed from the BIST file or filename), and the ship is going into a 1 kt current, the STW is 11 kts.

When STW is selected for plotting, the user enters a fixed current value (e.g., 1.5 kts) and selects ship direction as 'with' current (STW = SOG - current) or 'against' current (STW = SOG + current). Default will be 0 kt current (or groupbox for STW adjustment will be disabled).

[kjerram]

Added fixed current value, and files can be processed as batches 'into' or 'against' the current. May want to make this more flexible so that batches of files with both directions can be processed and plotted together. Perhaps add a right-click option for each file to select 'into' or 'against' current, along the lines of 'into the seas' selection provided for the RX Noise vs. Swell Direction (Azimuth) test.